Telecom Articles by Samir Amberkar: wp-lte-allocations-explained-p15

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3GPP Modem
Simulator

Test Your
Knowledge

LTE Allocations Explained

Table 7.1.7.2.2-1: One-layer to two-layer TBS translation table

TBS_L1	TBS_L2
. . . .

RNTI

RNTI stands for Radio Network Temporary Identifier. Below table lists down various RNTIs. Ref: [36.321:7.1].

RNTI

Value (hex)

Purpose

How do we get RNTI ?

RA-RNTI
Random Access

0001-003C

RAR

MAC calculates it while waiting for RAR
Ref: [36.321:5.1.4]

RA-RNTI = 1 + t_id + 10 . f_id

Temporary C-RNTI
Cell

0001-FFF3

UL msg3 transmission after receiving RAR

Received in RAR (MAC) message

C-RNTI
Cell

0001-FFF3

UL/DL allocations

Successful contention resolution during reception of L3 message, sent as a response to msg3, makes C-RNTI = Temporary C-RNTI

TPC-PUCCH-RNTI
TPC-PUSCH-RNTI
Transmit Power
Control

0001-FFF3

PHY UL power control

Configured by RRC (during reconfiguration procedure)

P-RNTI
Paging

FFFE

Paging, SI change notification

Constant specified in MAC standard [36.321:7.1]

SI-RNTI
System Information

FFFF

System information messages
(including SIB1)

Constant specified in MAC standard [36.321:7.1]

t
t
DCI formats

Rather than going through parameters of various DCI formats, we would look at DCI formats from allocation mechanism point of view. We would also try to map the allocation requirements that we listed earlier (on page 9) to DCI formats.

Earlier we said there are three ways to indicate resource allocation. The type is specified with 1 bit resource allocation header field ('0' for Type 0 and Type 1 otherwise). As there are three types, to specify it in DCI, we would need three bits, but when resource assignment is done for type 2, resource allocation header field is not included. This way 1 bit field is sufficient to indicate resource allocation type. This also imply that the DCI format can support either resource allocation type 0/1 or type 2.


Copyright © Samir Amberkar	Page 15 of 17